Just as a conductor coordinates several instruments in an orchestra to produce a symphony, breathing coordinates hippocampal brain waves to strengthen memory while we sleep, reports a new study from Northwestern Medicine.
This is the first time that breathing rhythms during sleep have been linked to these brain waves in the hippocampus; so-called slow waves, spindles and ripples -; in people. Scientists knew these waves were related to memory, but the underlying cause was unknown.
To strengthen memories, three special neural oscillations arise that synchronize in the hippocampus during sleep, but these were thought to come and go at random times. We discovered that they are coordinated by breathing rhythms.”
Christina Zelano, senior study author, professor of neurology at Northwestern University Feinberg School of Medicine
Northwestern scientists found that hippocampal oscillations occur at certain points in the breathing cycle, suggesting that breathing is a crucial rhythm for proper memory consolidation during sleep.
“Memory consolidation depends on the orchestration of brain waves during sleep, and we show that this process is closely timed by breathing,” said corresponding author Andrew Sheriff, a postdoctoral student in Zelano’s lab.
The study will be published December 16 in the Proceedings of the National Academy of Sciences.
The findings have important implications for disturbed breathing during sleep, such as sleep apnea, which is linked to poor memory consolidation.
We’ve all had better memories after a night’s sleep. This was noted as early as ancient Rome, when the scholar Quintillion wrote of the “curious fact” that “the interval of a single night will greatly increase the power of memory,” according to the study authors. He described what we now call memory consolidation, which is accomplished by the exquisitely tuned coordination of different brain waves in the hippocampus.
“When you sleep, your brain actively replays the experiences you had during the day,” Sheriff said.
Sheriff had just returned from a conference in Reykjavik, Iceland, where he had to learn his way around a new city. “The hippocampus plays an important role in forming a map of a new area,” Sheriff said. “I woke up and felt like I had a better representation of the city around me. That was made possible by the oscillations that happened during my sleep, which we discovered are coordinated by breathing.”
The study indicates that people with disturbed breathing during sleep should seek treatment for it, Sheriff said.
“When you don’t sleep, your brain suffers, your cognition suffers and you become foggy,” Sheriff said. “We also know that sleep-disordered breathing is linked to stroke, dementia and neurodegenerative diseases such as Alzheimer’s disease.
“If you listen to someone breathing, you may be able to tell when he or she is sleeping, because breathing happens differently when you sleep. One reason for this may be that breathing performs a careful task: coordinating brain waves that are related to each other. to memory.”
The study is titled “Breathing orchestrates the synchronization of sleep oscillations in the human hippocampus.”
Other Northwestern authors include Guangyu Zhou, Justin Morgenthaler, Christopher Cyr, Katherina K. Hauner, Mahmoud Omidbeigi, Joshua Rosenow, Stephan Schuele, and Gregory Lane.
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Magazine reference:
Sheriff, A., et al. (2024). Breathing orchestrates the synchronization of sleep oscillations in the human hippocampus. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.2405395121.